1. Field of the Invention
The present invention relates to a closing apparatus for twin pendulum hopper doors suitable for metering grain from a hopper trailer.
2. Brief Description of the Prior Art
A hopper trailer is a vehicle designed with one or more dropped hoppers below the trailer body. Each hopper has a bottom discharge opening through which material is gravity discharged. In the case of hopper trailers for use in hauling grain, a closing apparatus making use of pneumatically operated twin pendulum doors has been found effective. While a separate source of pressurized air could be used, it is preferred that the pneumatic system be operated off the vehicle""s air brake system where pressures tend to decrease with age of the vehicle. This is a problem for a pneumatic closing apparatus where the doors are closed with an extension spring.
Grain is typically unloaded into an augur or pit. When grain is unloaded from a hopper trailer, the operator may need to stop the flow or to adjust the rate at which the grain is flowing such that the flow of grain does not overrun the augur.
With a pneumatically operated closing apparatus having a spring return, there may not be enough pressure in an older vehicle""s air brake system to open the doors against the resistant of a spring stiff enough to close the doors against the flow of grain. Hence a closing apparatus that effectively meters the grain at first may stop working as the vehicle ages.
In view of the above, it is an object of the present invention to provide a compressed air closing apparatus for twin pendulum hopper doors wherein the discharge of material in the hopper can be regulated and accurately metered by the doors. It is another object to provide a compressed air closing apparatus whose performance is not substantially affected by a decline in available air pressure. Other objects and features of the invention will be in part apparent and in part pointed out hereinafter.
In accordance with the invention, a door closing apparatus is provided for a hopper with a bottom discharge opening for discharging material therefrom and first and second pendulum doors connected to the hopper that are moveable between a closed position preventing discharge of material from the hopper through the bottom discharge opening and an open position allowing discharge of material from the hopper through the bottom discharge opening. A framework is provided in the discharge opening for supporting the door closing apparatus.
The door closing apparatus has a first gear wheel mounted on a first shaft and a second gear wheel mounted on a second shaft, with the first and second shafts journaled in the framework in the discharge opening and with the first and second gear wheels having teeth in mesh. A torsion spring having first and second spring arms and an initial tension is attached by the first spring arm to one of said first or second shafts and the second spring arm is stopped from rotation by the framework.
A first crank arm is attached to the first gear wheel and a second crank arm is attached to the second gear wheel, with each of the first and second crank arms having a free end. A lever arm with a free end is attached to one of the first or second crank arms.
A first connecting link is pivotally attached to the free end of the first crank arm and pivotally attached to the first pendulum door and a second connecting link is pivotally attached to the end of the second crank arm and pivotally attached to a second pendulum door. The first and second crank arms are generally oppositely directed when the pendulum doors are in a closed position and are generally parallel when the pendulum doors are in an open position.
A bidirectional pneumatic cylinder with a piston rod for connection with a source of pressurized air is pivotally attached to the framework above the first and second gear wheels. The piston rod is pivotally attached to the free end of the lever arm.
In operation, the initial tension of the torsion spring damps movement of the pendulum doors by the pneumatic cylinder and resists opening of the pendulum doors if the pneumatic cylinder loses pressure.
The invention summarized above comprises the constructions hereinafter described, the scope of the invention being indicated by the subjoined claims.